Field of the Disclosure
Embodiments of the present disclosure generally relate to an electronic device, and more specifically, to a 3D memory cell.
Description of the Related Art
The heart of a computer is memory. The memory is typically used for storing programs, routines, a computer state, or other bits of information used in the operation and control of computers. Decreasing the size of computers has necessitated the reduction in the space available for memory cells while the requirements for larger memory capacity have continued to grow.
Phase change memory (PCM) is a type of non-volatile memory technology. PCM is an emerging technology and a candidate for storage class memory (SCM) applications and a serious contender to dislodge NOR and NAND flash memory in solid state storage applications and, in the case of NAND flash, solid-state drives (SSDs). PCM functions based upon switching a memory cell, typically based on chalcogenides such as Ge2Sb2Te5, between two stable states, a crystalline state and an amorphous state, by heating the memory cell. To heat the memory cell, an electrical current flows through the PCM cell.
PCM cells are arranged in an array, and each PCM cell is coupled with a selecting switch such as an ovonic threshold switch (OTS). Word lines (WL) and bitlines (BL) are arranged so that each memory cell can be programmed or queried. A row of PCM cells is activated by a single word line WL and each one of the PCM cells in that row will affect the bitline BL to which it is electrically connected according to the state of the PCM cells, i.e. according to the PCM cells being in their high (amorphous) or low (crystalline) resistance state.
The incorporation of 3D elements is difficult from a wiring perspective due to complexity. Electrically isolating each memory element and addressing adjacent devices that are not only separated in the lateral direction have proven to be problematic. The high density devices promote sneak currents between the elements that make reading the memory element difficult or inaccurate.
Therefore, there is a need for an improvement in the high density of devices in 3D memory.